The present disclosure relates generally to blade guard assemblies. In particular, blade guard assemblies for concrete saws that are designed to be reversibly mounted on either side of the saw are described.
The preparation of concrete pads is a common practice in the construction industry. Concrete pads are used in parking lots, roadways, as foundation slabs, in parks, patios, and any number of other building applications. Owing to its water-based nature, concrete naturally shrinks as it cures, due to the loss of water. This shrinking occurs first at the surface of the concrete, which is the location of water evaporation. Consequently, left to cure untended, concrete pads of sufficiently large size will develop cracks as they dry, which can compromise the concrete's integrity and mar an otherwise smooth surface.
One solution to prevent cracking during the curing process is to cut expansion gaps into the concrete surface early in the curing process, known as early entry cutting. These expansion gaps provide a space for surface tension to be relieved as the concrete further shrinks, thereby preventing cracks from developing in the slab. The concrete is typically cut from ¼ to ⅓rd of its depth. The timing of the cutting is critical; the concrete must cure sufficiently to withstand the weight of the concrete saw without marring its surface, but not have dried to the point where a saw requires water for cutting, or has begun to crack. Concrete at this point is known as green. Although a diamond masonry blade is used, due to the concrete still having relatively high water content, a saw cutting green concrete does not need water. As the concrete lacks the strength of fully cured concrete, the concrete saw must provide pressure against the concrete work surface immediately adjacent to the blade kerf to prevent spalling of the sides of the crack.
This pressure is supplied by a blade guard assembly attached to the concrete saw that houses the saw blade. The blade guard assembly also serves a safety function by substantially enclosing the rotating saw blade, and by channeling dust from the cutting action to keep the surrounding work area clear from the potential formation of dust clouds. The blade guard is typically immovably affixed to the concrete saw at the end of a drive shaft, to which is attached an arbor, to which the saw blade is further attached.
Known blade guard assemblies are not entirely satisfactory for the range of applications in which they are employed. For example, existing blade guard assemblies used on concrete saws employed in early entry applications are typically capable of being mounted on only one side of the saw. As concrete saws are bulky, walk-behind machines, having the blade assembly able to mount on only one side of a machine can pose problems on certain projects, such as when surrounding obstacles may prevent saw movement or not provide proper support for a clean cut. Often, being able to relocate the blade assembly to the opposite side of the machine will easily remedy these situations. The design of known blade guard assemblies tends to be unidirectional; mounting the blade guard on the opposite side of a machine may result in improper work surface contact and potential damage to the saw blade and green concrete. Consequently, operators of a saw that can accept a blade assembly on either side typically must carry a separate blade guard specific for each side of the machine, which increases costs.
A crucial part of the blade guard assembly is the blade shoe, through which the saw blade passes. The blade shoe serves as the contact point between the blade guard assembly and the work surface, and is the means by which pressure is applied to the work surface surrounding the blade kerf during cutting. The typical blade shoe configuration is substantially an elongated rectangular plate, with a centrally located slot through which the blade passes. Pressure supplied via the weight of the concrete saw and associated pressure devices is transmitted through the blade shoe to the work surface immediately surrounding the blade kerf.
In operation of the concrete saw, the blade shoe is subject to wear over time, which degrades both cut quality and blade life. As the concrete saw is moved forward in operation, the blade shoe slides upon the surface to maintain appropriate pressure. The blade cutting action generates dust, which is cleared from the cut primarily at the point where the blade rotates up out of the kerf. Depending on blade rotation, this point will be at either of the ends of the centrally located slot. This generated dust is abrasive in nature and, consequently, results in end of the centrally located slot wearing substantially faster than other portions of the slot, this wear being expressed as a noticeable widening of the slot. The widened slot, in turn, reduces the amount of pressure placed on the work surface immediately around the point where the blade is retreating from the work surface. Due to the retreating blade and dust ejection, this point is where opposing forces from the cutting action are at a maximum, and a slot that is widened due to wear is unable to effectively oppose these forces where they are immediately experienced. As a result, spalling of the work surface occurs, and due to the rougher cut, blade wear is increased with a commensurate decrease in blade life. Because the blade shoe is typically a single piece of cast or forged metal, a worn blade shoe must be replaced as a single piece, often at an elevated cost. Costs are further elevated by the fact that the blade and the shoe typically are replaced as a set; if the blade shoe wears, the blade must also be replaced, even if the blade would otherwise still have useful life.
Thus, there exists a need for blade guard assemblies and improved blade shoe designs that improve upon and advance the design of known blade guard assemblies and blade shoes. Examples of new and useful blade guard assemblies and blade shoes relevant to the needs existing in the field are discussed below.
Disclosure addressing one or more of the identified existing needs is provided in the detailed description below. Examples of references relevant to blade guard assemblies and blade shoes include U.S. Pat. No. 8,276,578. The complete disclosures of the above patents and patent applications are herein incorporated by reference for all purposes.